• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.102.2-102
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• 2002

In this paper, the improved Multi-FNN (Fuzzy-Neural Networks) model is identified and optimized using HCM (Hard C-Means) clustering method and optimization algorithms. The proposed Multi-FNN is based on FNN and use simplified and linear inference as fuzzy inference method and error back propagation algorithm as learning rules. We use a HCM clustering and genetic algorithms (GAs) to identify both the structure and the parameters of a Multi-FNN model. Here, HCM clustering method, which is carried out for the process data preprocessing of system modeling, is utilized to determine the structure of Multi-FNN according to the divisions of input-output space using I/O process data. Also, the parame...

• 대한전기학회논문지:전력기술부문A
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• 제48권11호
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• pp.1441-1447
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• 1999

A discrete time domain modeling is presented for the pulse-width modulated series resonant converter (PWM-SRC) with a discontinuous current mode. This nonlinear system is linearized about its equilibrium state to obtain a linear discrete time model for the investigation of small signal performances such as the stability and transient response. The usefulness of this small signal model is verified through the dynamic simulation.

• 한국구조물진단유지관리공학회 논문집
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• 제17권4호
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• pp.1-8
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• 2013

철근콘크리트 구성요소에 대한 비탄성 거동 모델 개발은 철근콘크리트 구조물에 대한 성능기반 내진평가의 정밀도 향상에 있어 매우 중요한 요소로 본 연구에서는 지진과 같은 불규칙 반복 하중에 대한 철근콘크리트 구조물의 비선형 동적응답을 예측함에 있어 콘크리트 구성모델의 특성에 따른 민감도를 고찰하고자 하였다. 해석결과에 따르면 구속된 코어 콘크리트 모델과 일반 콘크리트의 구성모델은 동적응답에 큰 영향을 끼치지 않았으나 철근의 경우에 층간변위와 관련하여 구성모델에 따른 동적거동은 매우 민감하게 응답하는 것으로 나타났으며, 몇 개 층에서의 층간변위는 그 차이가 철근 구성모델 선택에 따라 2배 이상 차이 나는 것으로 나타났다. 따라서 Non-ductile과 Ductile 골조 공히 비선형 동적해석을 수행하는데 있어 정밀한 철근 구성모델의 선택은 매우 중요한 것으로 사료된다.

• 제어로봇시스템학회논문지
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• 제7권1호
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• pp.1155-1161
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• 2001

We propose an adaptive nonlinear control algorithm for high precision tracking and stabilization of LOS(Line-of-Sight). The friction parameters of the LOS gimbal are estimated by off-line evolutionary strategy and the friction is compensated by estimated friction compensator. Especially, as the nonlinear control input in a small tracking error zone is enlarged by the nonlinear function, the steady state error is significantly reduced. The proposed algorithm is a direct adaptive control method based on the Lyapunov stability theory, and its convergence is guaranteed under the limited modeling error or torque disturbance. The performance of the pro-posed algorithm is verified by computer simulation on the LOS gimbal model of a moving vehicle.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.423-423
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• 2005

A carbon nanotube-based nanoelectromechanical device in resonance is examined theoretically. Mechanical deflections are electrically induced and resonantly excited at the fundamental frequency in cantilevered carbon nanotube. The electrically conducting elastic beam with van der Waals interactions at the tip is used for the modeling of the carbon nanotube device. Due to the elastic, electrical, and van der Waals interactions, the total energy of the system shows the unsymmetric two-well potentials. The predictions can be made that the device exhibits its nonlinear dynamic features in the two-well potentials. Also it is predicted that the fundamental frequency of the carbon nanotube device was changed by the nonlinear interactions induced by electrical and van der Waals potentials between carbon nanotube and ground surface of the device.

• 조명전기설비학회논문지
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• 제23권7호
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• pp.29-40
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• 2009

This paper proposes a modeling and controller design approach for a hybrid wind power generation system that considers a fixed wind-turbine and a dump load. Since operating conditions are kept changing, it is challenge to design a control for reliable operation of the overall system To consider variable operating conditions, Takagi-Sugeno (TS) fuzzy model is taken into account to represent time-varying system by expressing the local dynamics of a nonlinear system through sub-systems, partitioned by linguistic rules. Also, each fuzzy model has uncertainty. Thus, in this paper, a modem nonlinear control design technique, the sliding mode nonlinear control design, is utilized for robust control mechanism In the simulation study, the proposed controller is compared with a proportional-integral (PI) controller. Simulation results show that the proposed controller is more effective against disturbances caused by wind speed and load variation than the PI controller, and thus it contributes to a better quality wind-hybrid power generation system.

• Steel and Composite Structures
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• 제50권6호
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• pp.643-658
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• 2024

The main aim of this study is to quantify the code seismic design coefficients of the RCS system, which consisted of reinforced concrete columns and steel beams, based on the FEMA P-695 methodology. The underlying intention is to evaluate the seismic performance of the RCS system at the system level rather than the connection level. A set of 24 archetype buildings with a various number of stories, beam span lengths, gravity load levels, and seismic load levels are selected and designed based on the prevailing code requirements. Nonlinear analytical models are developed and validated by experimental tests. The pushover and response history dynamic analyses are conducted to evaluate the required data in the performance quantification process. The results show that the design coefficients suggested by the code are acceptable. However, the level of conservatism is very high. Thus, it is possible to use a larger R-factor in the design process or make some relaxations in the design requirements related to this structural system.

• Steel and Composite Structures
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• 제19권1호
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• pp.237-262
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• 2015

In this study, we try to compare different intensity measures for evaluating nonlinear response of bridge structure. This paper presents seismic analytic fragility of a three-span concrete girder highway bridge. A complete detail of bridge modeling parameters and also its verification has been presented. Fragility function considers the relationship of intensities of the ground motion and probability of exceeding certain state of damage. Incremental dynamic analysis (IDA) has been subjected to the bridge from medium to strong ground motions. A suite of 20 earthquake ground motions with different range of PGAs are used in nonlinear dynamic analysis of the bridge. Complete sensitive analyses have been done on the response of bridge and also efficiency and practically of them are studied to obtain a proficient intensity measure for these types of structure by considering its sensitivity to the period of the bridge. Three dimensional finite element (FE) model of the bridge is developed and analyzed. The numerical results show that the bridge response is very sensitive to the earthquake ground motions when PGA and Sa (Ti, 5%) are used as intensity measure (IM) and also indicated that the failure probability of the bridge system is dominated by the bridge piers.

• Earthquakes and Structures
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• 제12권2호
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• pp.165-175
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• 2017

This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full probabilistic analysis methods like MC commonly are very time consuming, the feasibility of simple approximate methods' application including First Order Second Moment (FOSM) method and ASCE41 proposed approach for the soil uncertainty considerations is investigated. By comparing the results of the approximate methods with the results obtained from MC, it's observed that the results of both FOSM and ASCE41 methods are in good agreement with the results of MC simulation technique and they show acceptable accuracy in predicting the response variability.

• 한국정보통신학회논문지
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• 제8권1호
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• pp.18-27
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• 2004

본 논문에서는 다 채널 무선전송시스템에서 RF증폭기(SSPA)의 비 선형과 백-오프동작에 따른 기저대역 디지털변조신호의 왜곡을 분석하였다. OFDM 다 채널 무선전송시스템에서 적용되는 SiGe HBT의 바이어스 전류를 가변 시켜 설계한 SSPA의 비 선형 전력전달함수를 구하고 이 전달함수에 수학적으로 비 선형 모델링 함수와 비교 분석함으로서 최적 바이어스조건을 구하였다. RF 증폭기에 입력전력을 가변 시켰을 때 SSPA의 대역-내에서의 출력전력과 대역-외에서의 출력전력을 구했으며, 입력전력에 따른 디지털 변조신호의 성상도 왜곡을 분석하였다. 본 연구의 결과는 선형동작을 위한 RF증폭기의 적응바이어스 설계와 선형화를 위한 SSPA의 백-오프 동작 최적 바이어스를 결정하는데 매우 유용하게 응용될 수 있다.